1. Field of the Invention
The present invention relates generally to ultraviolet lighting devices. More particularly, the invention concerns an ultraviolet fixture that uniquely provides for three separate ultraviolet wave lengths within one lamp enclosure.
2. Discussion of the Invention
Ultraviolet lighting devices are commonly used in scientific, medical industrial, and educational applications to elicit a reaction from a specimen exposed to the ultraviolet radiation (UV). Ultraviolet light is electromagnetic radiation in the region of the spectrum located between X-rays and visible light. It is divided into three principal ranges: 1) UV-A, or long wave, 2) UV-B, or mid-range, and 3) UV-C, or short wave. For each of these UV ranges specific applications have been developed, and new applications are continuously being developed.
To obtain a desired ultraviolet wave length, the fluorescent style tube is most commonly used. The fluorescent tube is an electric discharge device that uses a low pressure mercury vapor arc to generate ultraviolet energy. The ultraviolet energy released in typical, commercially available fluorescent tubes is primarily at the wave length of about 254 nanometers. In general, this ultraviolet energy is converted into other ultraviolet wave lengths by the use of phosphors which have the ability to absorb the ultraviolet energy and re-radiate it in other wave lengths. For example, long wave ultraviolet of about 365 nanometers and mid-range ultraviolet of about 300 nanometers are created by coating the inside of the fluorescent tubes with the proper phosphor(s) which convert the short wave ultraviolet. The envelope of the tube is also typically made of a glass that inhibits the passage of the short wave ultraviolet. To obtain a short wave ultraviolet tube, a special glass that transmits about 254 nanometers is generally used, and no phosphor is required.
In the past ultraviolet irradiation of selected specimens has been accomplished using a single UV range fluorescent tube mounted in either a metal or plastic enclosure. To eliminate extraneous ambient white light generated by the UV tube, a UV transmitting filter/ambient light blocking filter, is typically mounted in front of the UV tube. When it was desired to obtain two UV ranges (wave lengths) from a single enclosure, two UV tubes emitting two levels of UV radiation were generally mounted side by side within the enclosure, and an appropriate filter was placed in front of each tube.
When it was necessary to illuminate a large area with a UV range (wavelength), several fluorescent tubes of the same UV range were typically placed side by side within a large fixture having the proper electrical ballast to power the tubes. In these instances, a large piece of UV transmitting/ambient white light blocking filter was typically placed in an opening through which the UV light was transmitted.
Because of the side by side mounting of the fluorescent tubes in the prior art, UV irradiation devices, the devices were unnecessarily large, bulky, and difficult to transport and store. Further, when the specimen was to be irradiated by several different ranges of UV radiation, either separate fixtures had to be used or fixtures having complex filtering, switching and power supply requirements were needed.
Exemplary of prior art devices of which Applicant is aware that may have some pertinence to the present disclosure, are those disclosed in U.S. Pat. No. 4,015,353, issued to Zarfat, and U.S. Pat. No. 4,002,022, issued to Lopez. The Zarfat patent relates to an advertising display device while the Lopez patent refers to a rotating electro-mechanical sign.